The human digestive system functions to extract the nutrients stored in the foods you eat and make them available to the cells, tissues and organs throughout your body. Digestion is a process in which you break down foods and beverages into their smallest components so that your body can use them for nourishment and energy.In essence, the digestive system involves four phases: ingestion, digestion, absorption and elimination.
Ingestion
Ingestion is the process in which you consume foods, chew them into smaller pieces and swallow the bolus. As you chew your food, enzymes within your mouth begin to digest the various components and break down larger compounds, particularly carbohydrates, into smaller sugar compounds and molecules. You also enjoy the taste of foods during this phase. When you swallow your food, it passes through your esophagus and into your stomach. Ingesting nutrient dense foods, such as fruits and vegetables, may reduce your risk of chronic diseases, whereas ingesting unhealthy foods, such as processed and fast foods, may increase your risk of heart disease, hypertension, cancer, diabetes and osteoporosis.
Digestion
Digestion is a process within your stomach in which you break down all of your food components into small molecules that your body can absorb and utilize. Stomach and pancreatic enzymes break down carbohydrates, proteins and fats. Amylase and maltase, break down carbohydrates into simple sugar molecules, such as glucose, fructose and galactose. Trypsin and pepsin are enzymes that break down proteins into amino acids and lipases are enzymes that break down fats into fatty acids and glycerol. Carbohydrates usually take the least amount of time to digest and fats take the longest. If you have lactose intolerance, you may have insufficient levels of lactase, the enzyme that breaks down lactose, the sugar in milk.
Absorption
Absorption is a process where the cells within your intestine absorb single glucose, amino acid and fatty acid molecules for transport into your blood and liver. Your liver controls which nutrients will be utilized and transported to the rest of your body or stored for future use. The release of sugar into your blood can affect how much insulin your pancreas releases to help transport glucose into your skeletal muscle cells to be metabolized for energy. Eating high glycemc foods, such as white rice, may rapidly increase the absorption of glucose into your blood and increase your risk for insulin resistance, diabetes and cardiovascular disease. Consuming foods that are high in soluble fiber, such as beans and apples, may reduce the amount of dietary cholesterol that you absorb and reduce your risk of heart disease.
Elimination
Elimination is the process by which your body removes components of foods that you do not need. Insoluble fiber is not digested, but helps you move the waste through your digestive tract and out of your body. Insoluble fiber also reduces your risk of constipation. It is found in wheat bran and vegetables.
References
- National Institute of Diabetes and Digestive and Kidney Diseases: Your Digestive System and How It Works
- United States Department of Agriculture: Dietary Guidelines for Americans 2010
- MayoClinic.com: Lactose Intolerance
- Linus Pauling Institute at Oregon State University: Glycemic Index and Glycemic Load
- MayoClinic.com: Dietary Fiber: Essential for a Healthy Diet
